Process for the production of graft polymers of high rubber content

Abstract

The invention relates to a process for the production of graft polymers of resin-forming monomers on a rubber in which a very high graft yield is obtained by the use of an initiator system of an organic hydroperoxie and ascorbic acid. The graft polymers obtained are suitable as thermoplastic molding compositions or as constituents thereof.

We claim: 
     
       1. A process for the production of a graft polymer which comprises the emulsion graft polymerization of: (a) from 40 to 90%, by weight, of an at least partly cross.linked diene rubber having an average particle diameter of from 0.1 to 0.6 μm; and   (b) from 60 to 10%, by weight, of one or more of styrene, acrylonitrile and methyl methacrylate; an initiator system comprising an organic hydroperoxide and ascorbic acid being used and a graft yield of greater than 60%, by weight, being obtained.   
     
     
       2. A process as claimed in claim 1 wherein from 50 to 80%, by weight, of (a) and from 50 to 20%, by weight, of (b) are emulsion graft polymerized. 
     
     
       3. A process as claimed in claim 1 wherein the graft polymerization of (b) is carried out in aqueous emulsion in the presence of an emulsion of (a) at a temperature of from 40° to 70° C. using an initiator system of from 0.3 to 1.5 parts, by weight, of organic hydroperoxide and from 0.1 to 1 part, by weight, of ascorbic acid per 100 parts, by weight, (b) in a weight ratio of from 0.3:1 to 15:1.